The invention relates to a profiled shaft for anchoring a hip-joint prosthesis in the femur, with a shaft section and a fixation section, formed at the end of the shaft section, which serves for the fixation of a spherical joint head, wherein the medial narrow side of the shaft section merges with a continuously curved arch that ends in the region of the fixation section, and wherein the lateral side of the shaft section in its proximal region merges with a trochanter wing on which the corners are beveled to form slanted surfaces (facets).
A profiled shaft of this kind for anchoring a hip-joint prosthesis in the femur is known, for example, from U.S. Pat. No. 5,456,717.
The purpose of the beveled surfaces (facets) is to achieve a better fit of the trochanter-wing region of the profile shaft when it is seated in the femoral opening.
The conventional practice is to use a facet angle of 45xc2x0 or 135xc2x0 (angle between the plane of the lateral side and the plane of the adjacent facet of interest).
However, this specification of the facet angle has proved to produce comparatively large empty spaces in the corner regions of the trochanter wing.
The object of the present invention is to create a profiled shaft of the above-mentioned kind, for the anchoring section of a hip-joint prosthesis in the femur, such that the empty space in the trochanter-wing region can be substantially reduced by particularly simple measures.
This object is achieved in accordance with the invention by developing the profiled shaft of the kind cited above in such a way that the angle between the plane of a beveled surface (facet) and the plane of the adjacent lateral side surface is made smaller than 135xc2x0 and larger than 90xc2x0.
An especially advantageous and effective embodiment of the invention further consists in restricting the above-mentioned angle to the range between 100xc2x0 and 120xc2x0.
Furthermore, an especially improved filling of the empty space in the trochanter-wing region can be achieved by forming a beveled surface (facet) at the transition between the lateral surface of the shaft and the anterior (broad) surface, and between the lateral surface of the shaft and the posterior (broad) surface of the shaft.
The invention is further characterized in that the beveled surfaces are constructed as facets with unequal angles at their two ends.
An especially advantageous embodiment of the invention, in the case of a profiled shaft in which the shaft section on its lateral aspect merges with the trochanter wing in the form of a continuously bending curve, consists in a change in the configuration of each of the beveled surfaces in the region of the continuously bending curve, such that in the direction from the shaft region to the trochanter region an equal-angled facet changes to one with unequal angles.
In this case the change from equal-angled facet to unequal-angled facet can take the form of a gradual transition or, in an alternative embodiment, there can be a stepwise change from equal-angled facet to unequal-angled facet.